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Change To Syn Gear Oil Now!

73K views 268 replies 95 participants last post by  markthomas1969 
#1 ·
Lots of people mention the subject, but maybe it needs it's own thread.

Change your gear oil to synthetic as soon as you can. I used Mobil 1. One gentleman (he inspired me) used Redline. It might be better but its hard to find, here.

Keep the car level (no ramps, you can reach the drain) and drain every drop of the old oil. Mine only has a few K miles on it. Since my car is lowered, I needed my skinny son to get at the drain plug. Don't lose the washer!

You'll need a long a$$ funnel. Then dump in that Mobil 1.

I think the owners' manual is wrong in the capacity. It calls for 3.75 quarts. I used 4.

Then go for a drive and be prepared for a seriously dramatic change in your shifting and transmission behavior. It's hard to believe it's the same machine.

Go figure.

:) :)
 
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#153 ·
subieracer18 said:
so scooby 24, are you still using the gm synchromesh? if so how is it

Well I traded in my WRX and got an STi and am still using stock fluid as it hasn't caused any problems yet but when I traded it in the tranny was feeling a bit sloppy so the fluid was needing to be changed after about 10k miles. So I think it's okay to run for about 10k but then it needs a change.
 
#154 ·
I used to be big into racing Pontiac Fieros. The manual trans cars use either 5w-30 engine oil or GM's Syncromesh. Being a mid engine car the tranny has never been described as smooth but I could tell the difference when using one over the other. Anyway, it was typical for me to change the tranny oil every 15k miles. Even the honduh boyz are loving the Syncromesh.
I recently changed my fluid to 80w90 GL-5 and its terrible when cold. I will be switching to Syncromesh or Royal Purple at the next service.

Steven

BTW filled the Skylines tranny with Redline LW MTL and is was smooth as butter!
 
#157 ·
alrighty then,
Will pennzoil 80w90 work in the tranny? i was going to put 2.75 quarts of the 80w90 and 1 quart of pennzoil synchromesh in the tranny. Will the mobil 1 synthetic work in the rear diff? or better yet will the synchromesh work in the rear diff.
 
#158 ·
Try not to go with 80w90 :thumbdown its way too thick when cold. Its been near freezing here for the last week and I HATE the first 10 minutes of driving. I have to be at a complete stop before downshifting into 1st and its NEVER down that before the fluid change. I am draining that Penzoil crap out during my next oil change (200 miles!).
 
#160 ·
you can use straight 75w90NS Redline and call it a day,
you can use 50/50 of the above and MT90 and have a tranny lube that will shift even smoother in cooler weather,
you can use a mixture of 75w90NS and/or MT90/Synchromesh and get comparable results to the second mixture.
MT90 and synchromesh I believe are not that different therefore I don't expect the end result to change much
 
#163 ·
Bump! I need updates. I'm at around 11k miles and I've decided it's time for me to change out the gear oil in the STi.

Here's what I'd like to go with and would like to know if anyone has any updates on these combos:

Redline 75w90NS (since it's GL-5) and Synchromesh mix

Redline Shockproof lightweight

These are the two routes i'm considering but am leaning towards the shockproof lightweight. I know many have used this so does anyone have anything to add about that oil?
 
#164 ·
The Shockproof keeps the ring and pinion from experiencing shock-loading damage, especially true when drag racing. For street use, no difference, for autocross some benefit, for track use quite useful, for drag strip might as well use the Heavy Duty Shock proof. The later effectively becomes a 250-weight gear lube via microscopic additives that help the lube from getting "squeezed" out during high loads
 
#165 ·
99OneLE said:
The Shockproof keeps the ring and pinion from experiencing shock-loading damage, especially true when drag racing. For street use, no difference, for autocross some benefit, for track use quite useful, for drag strip might as well use the Heavy Duty Shock proof. The later effectively becomes a 250-weight gear lube via microscopic additives that help the lube from getting "squeezed" out during high loads
Alright...well many people are experiencing 5th gear grinding in STi's and one guy used Shockproof lightweight and got rid of the grinding completely. That tells me the gear is better for synchros than stock plus it's OBVIOUSLY going to be better at shock loading than stock....so it sounds like a winner to me.

Is it GL-5 rated...or does that not even matter since the stuff is so tough...?
 
#166 ·
Notice I said ring and pinion, so it's good in the diff, not the tranny/front axle combo.
There you want to use GL5 spec. Redline 75W90NS, or MT90 GL4 spec that is better in cold weather. I actually run a 50/50 mix. The synchromesh is probably ok, I don't see any problems with some of it in the case, but 100% synchromesh concerns me, since it's not GL 5 rated, as far as I can tell.
Remember the transaxle houses the synchros and the front diff, so you need to address the needs of the synchros first, and that is no limited slip fluids. Also nothing to thick or you will not be able to shift in cooler weather.

Do you use the car on the track?
If so then simply replace fluids often, depending on the number of track events.
On the street, outside of drag racing all the time, it will be very very difficult to see the difference in all the lubes mentioned above. Besides drag racing will destroy way more than the tranny.
 
#167 ·
Redline shockproof IS GL-5 rated. Redline warns that it actually may be too slippery for trannys BUT a lot of people have had good luck stopping grinding with it. Dunno why. Fixed my buddy's Impreza L 3rd gear grind, and I had good luck with it in my WRX (though I didn't have any grinding to start out with.

I also reckon shockproof is just about the best stuff out there for the rear end.

C
 
#168 ·
GV27 said:
Redline shockproof IS GL-5 rated. Redline warns that it actually may be too slippery for trannys BUT a lot of people have had good luck stopping grinding with it. Dunno why. Fixed my buddy's Impreza L 3rd gear grind, and I had good luck with it in my WRX (though I didn't have any grinding to start out with.

I also reckon shockproof is just about the best stuff out there for the rear end.

C
Chris I can't find GL ratings for any of the shockproof- linky?

Thanks

Mike
 
#169 ·
ShockProok is fine for open and limited slip diffs, so it makes sense it's GL5 spec lube.

It also makes senses that it might not have the optimum friction properites for our synchros. I'm worried that not using the right lube for the synchros might improve things for a while but will also cause the synchros to wear faster.
 
#170 ·
Big Sky WRX said:
Chris I can't find GL ratings for any of the shockproof- linky?

Thanks

Mike
I already posted those somewhere on this site and on the nabisco. If you look around long enough on Redline's site they have a pdf that lists it as GL-5.
 
#172 ·
Retro said:
I already posted those somewhere on this site and on the nabisco. If you look around long enough on Redline's site they have a pdf that lists it as GL-5.
Ya know, I saw that same PDF. But when I went looking for it in reference to this thread I couldn't find it again. I wonder if it was a typo?? I just emailed them......I'll let you know what I find out.

C
 
#174 ·
Here's the response from Redline:

Thank you for contacting Red Line Oil, the ShockProof is a special race type lubricant and doesn't carry a GL rating, though they should provide the GL-5 protection levels. The tech report doesn't mention a specific GL rating.

In the WRX transaxle we recommend the 75W90NS and the 75W90 in the rear differential, both are GL-5 gear oils.

Regards, Dave
Red Line Oil
 
#176 · (Edited)
scooby24 said:
I got the same response from them but many people have had problems with 75w90ns and synchros so I'm going to go ahead and go with shockproof lightweight
Are you sure those problems were with NS and not the regular stuff? I catch many people getting confused with NS and the regular version. I actually have the PDF saved that mentions the GL rating of Shockproof.. maybe someone lied or was misinformed. I'll look for it and repost it.

Edit: Found it on the last page where they list all the individual oils http://www.redlineoil.com/whitePaper/18.pdf They list Lightweight and SuperLightweight as being GL-5.
 
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